Title: The nature of the L/T transition; variability in cool brown dwarfs

Abstract:
We propose to monitor a statistically significant sample of L/T type
brown dwarfs to determine levels of variability due to dynamic
atmospheric processes such as dust cloud formation and destruction.
Understanding the behavior of dust clouds is critical to our overall
understanding of this class of brown dwarfs. Recent observations and
models suggest that the transition from L to T may be due to the rapid
evolution of dust clouds. Such models also imply significant levels of
variability. In coordinated proposals, we will make a definitive study
of this variability on baselines of up to 15 hours, significantly
building on our previous work. The large size of our sample is critical
to obtain a true measure of variability levels in the L/T brown dwarf
population, and will permit us to verify or refute the models of the L/T
transition in brown dwarfs.